Cervical orthosis is used to immobilize the neck in various disorders such as trauma and post-operation. However, it is still uncertain how cervical orthosis restricts the degree of movement of the cervical spine during swallowing and how they affect swallowing physiology. The purpose of this study was to evaluate these issues using the Philadelphia(®) Collar. We conducted videofluorography of swallowing in 39 healthy subjects (23 men, 16 women; mean age of 34.3 years) with and without cervical orthosis. To compare the two conditions regarding the cervical spine motion, we determined the angular and positional changes of the occipital bone (C0) and each cervical vertebra (C1-C7) from the oral phase to the pharyngeal phase. Similarly, to compare swallowing physiology, we assessed the start and end times and the durations of soft palate elevation, rapid hyoid anterosuperior movement, epiglottis inversion, closure of the laryngeal vestibule, and pharyngoesophageal segment (PES) opening. Finally, we compared the transit times of contrast agent in the two conditions. The respective extensions of C1, C2, and C3 were 0.31°, 0.07°, and 0.05° (mean) with cervical orthosis, and the respective flexions of C1, C2, and C3 were 0.98°, 1.42°, and 0.85° (mean) without. These results suggested that cervical orthosis restricted the flexion of C1-C3. Analysis of swallowing physiology revealed that the average durations of hyoid anterosuperior elevation, epiglottic inversion, and PES opening were prolonged by 0.09, 0.19, and 0.05 s, respectively. In conclusion, the cervical orthosis restricted the movement of the cervical spine during swallowing and changed swallowing physiology.
Keywords: Cervical orthosis; Cervical spine motion; Deglutition; Deglutition disorders; Dysphagia; Swallowing; Swallowing physiology.